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HDD 2018-19 A
HDD (Hard Drive Disk) - Emanuele Cocuzza HDD (Hard Drive Disk) is a low cost, high capacity storage component of a computer. Its first version was created in 1956 by IBM and it was called RAMAC (Random Access Method of Accounting and Control). It had the size of a refrigerator and it required an entire room to operate it, with the cost of $10,000 per megabyte to store information. Six years later the price went down to $640 per megabyte, which is still an enormous cost compared to the one we are used to have nowadays. With this kind of price, an Iphone would have a cost of approximately 20.5 million $ a month. Fortunately throughout the years the major advancement in technology made HDD a lot more efficient and less expensive, and it has been since a long time a major and important component of almost every type of computer. A HDD records data by magnetizing a thin film of magnetic material on a disk. Different sequential changes in the direction of magnetization represents the data in form of binary bits. The data is read by the disk which detects the changes and transition in magnetic fields. The data of the user is encoded using a scheme that determines the different magnetic transitions of the data. Hard Disk Drives store or write data and informations in tiny magnetic fields called fluxes, which constantly switch forth and back in a process called flux reversal. HDD reads flux reversal at a very high speed when storing data. Usually a HDD structure consists of a spindle that holds a flat circular disk, which is most of the times referred as platter. The platter is made of aluminium or glass material and it holds the recorded data, and it is covered with a thin layer of magnetic material which has a thickness a approximately 3 micro inches (0.000003 inches), much less thicker than a piece of paper (0.004 inches). Modern HDD have platters that spin at speeds varying from 4,200 rpm to 15,000 rpm depending on the energy-efficient ratio of the device. Informations and data is written and to read from the platters that rotates as it rotates as past device called read-and-write heads. Those components are positioned in a way that they can operate close to the magnetic surface of the platter to read or write all the magnetic field changes that can store the data. The read-and-write heads detect or modify the magnetization of material passing under them on the platter, turning them into data and informations. Read-and-write heads are located on the head arm or head sliders, which hold them in the way that allows them to read the magnetic information on the platter. The spindle motor is responsible for the rotation of the platter and it can rotate at a speed varying from 3600 rpm to 7200 rpm depending on the power of the device. On modern HDDs, a intelligent circuit board is built to the hard disk, creating an interface between the hard disk drive and the computer, also containing electronic components that control various section of the hold. Most of Hard Drive Disk have two air filters, called Recirculating Air Filter and Breather Filter. These allow clean air to circle into system and to make sure dust is not collected inside the structure. Cables and connectors are used to attach the structure of the HDD to the Motherboard. When compared to other data storage devices, HDD has pros and cons. It has a cheaper cost and a better capacity than SSD (Solid State Drive), which on the other hand has a better performance in terms of noise, vibration, production of heat, failure rate or copy/write speed. The data in the computer is also stored in the RAM while it is being used on the device. RAM is temporary storage from the computer short memory that stores information while your are working on it, while on HDD it is possible to store a lot heavier and long term data. Sources: * https://www.pcworld.com/article/127105/article.html * https://www.itschool.gov.in/PDF/SITC%20hardware%20training/Hard%20disk.pdf * https://www.utica.edu/faculty_staff/qma/harddrive.pdf * https://www.storagereview.com/ssd_vs_hdd * https://www.backblaze.com/blog/whats-diff-ram-vs-storage/